I might be able to help them as I am in Bucks too, can you tell me more where in Bucks they are privately if you get consent from parents to discuss? I think language wise, it would be useful to do lots of semantic relationships activities to strengthen the word retrieval and to speed up the process. I have seen children with similar profile before in the community, but they have more complex medical background. Does the child have a paediatrician and is he known to neurology anywhere?
I am also PROMPT trained if that helps, so can also look into that. Happy to talk to you over the phone. Let me know what is helpful.